1. Field of the Invention
The present invention relates generally to a bearing and distance indicating unit for use in a vehicle. More particularly, the invention relates to a travel route indicating apparatus for use in an automotive vehicle or the like which is adapted to sequentially indicate travel conditions of the vehicle at any given moment, such as the current location, path of travel, direction of travel, etc.
2. Description of Relevant Art
In attempting to prevent the driver of an automotive vehicle or the like from becoming lost such as when driving at night or in unfamiliar places, there have been developed a variety of apparatus designed to indicate continuously or discretely a current location of the vehicle or similar information by way of an indication panel or display screen, including a related road map or the like, disposed adjacent the driver's seat. The driver is thus provided with ready guidance relating to the vehicle's status of travel at any given moment with respect to a desired course of travel.
The conventional travel route indicating apparatus is constructed such that a travelling distance of a vehicle at any given moment is detected in accordance with its speed of travel and time by a distance detecting section, a current bearing and the amount of azimuthal deviation of the vehicle at the given moment are detected by a bearing detecting section employing a rate gyroscope or the like adapted to detect a possible angular velocity produced about the axis of yawing of the vehicle, the location of the vehicle along its travel route at that moment is obtained from an arithmetic operation performed on the thus-detected data, and the results are indicated by way of spot information varying from time to time on a display which indicates a suitable road map of routes or roads on which the vehicle travels.
With the conventional arrangement as described above, however, it is very possible that spot information showing a current location of the vehicle on the display would deviate from a predetermined course of travel due to an accumulated error in detection resulting from a possible drift of the gyroscope while the vehicle is travelling, to such an extent that such information would indicate an erroneous location of the vehicle on the display screen which includes a map of complicated and crowded roads and streets. Therefore, it is very difficult if not impossible for the driver of the vehicle to determine whether the displayed information on the screen is erroneous or if his vehicle is actually travelling along a different or wrong course, thus resulting in substantial ambiguity.
The present invention is essentially directed towards overcoming the foregoing inconvenience and difficulties attendant the conventional travel route indication apparatus, which problems have not heretofore been satisfactorily overcome.